1. Field of the Invention
The present invention relates to a method of fabricating a semiconductor optoelectronic structure, especially to a fabricating method that can integrate conventional semiconductor technology to form a semiconductor optoelectronic structure.
2. Description of the Prior Art
Along with the improvement of technology and the requirement of great data transmission in modern society, conventional copper cables are less capable of carrying more and more signals to travel a long distance due to the physical limitation of electrical resistance and signal delays. Naturally, optical fibers meet the demand of carrying very large information to travel a very long distance so they replace the conventional copper cables to be the medium of long distance carrier of information because one single optical fiber allows multiple beams of light of different wavelengths, each carrying different information to travel at the speed of light without mutual interference and without attenuating too much after traveling an extreme long distance. Substituting copper cables with optical fibers has been the main trend in the present years.
However, present semiconductor devices still use electrons to transmit signals. If we want to integrate optical signals into conventional integrated circuit (IC) structure, a well-designed optical transmission system is needed to serve as a converting system between the optical fiber transmission system and the copper cable transmission system. The optical transmission system usually includes a light waveguide, a light transformer, a light modulator, a photo-detector or other devices that are able to transmit, to separate, to combine optical signals, or to process electrical/optical switching. A light transformer can receive outside optical signals and, by its special material or three-dimensional shape, can couple the signals into the light waveguide. A light waveguide can transmit the optical signals in conventional semiconductor medium and by using different materials of different refractive index between the transmission medium and the coating medium, the light transmission integrity can be retained. Lastly, the optical signals are converted into a general electrical current message, accessing to electronic devices for the subsequent signal processing.
In current optical transmission system, the biggest problem lays in the depletion of optical signals resulting from the optical coupling effect between each optical device. For example, a conventional light transformer is usually formed in advance, and then each of the transformers is bonded onto the semiconductor substrate respectively. In detail, after forming the light waveguide, the already-formed light transformer is aligned and bonded onto the light waveguide by using an adhesive. However, the adhesive can easily contract when curing, and because of the different spreading effects due to different composition of the adhesive, the coupling effect between the light waveguide and the light transformer will decrease, affecting its transmission quality. In addition, the current trend of development optical transmission system is to integrate it into the existing semiconductor substrate, such as a semiconductor substrate including a CMOS disposed therein. Therefore, effectively integrating the optical components and semiconductor components by using existing semiconductor technologies to form an optoelectronic structure on the substrate remains a problem to be solved.